Hip joint device and method

ABSTRACT

A medical device for implantation in a hip joint of a patient is provided. The medical device comprising a first piece being adapted to be fixated to the femoral bone and a second piece adapted to be fixated to the pelvic bone. The medical device further comprises a releasing which in a first state is adapted to hold said first piece attached to said second piece, and in a second state release said first piece from said second piece. The releasing member is adapted to change from said first state to said second state when a predetermined strain is placed on said releasing member by the connection with the first or second piece. The medical device further comprises a calibration member for calibrating the pre-determined strain required for said releasing member to change from said first state to said second state.

This application is a continuation of U.S. patent application Ser. No. 13/383,024 filed Jan. 9, 2012, which is the U.S. national phase of International Application No. PCT/SE2010/050806, filed Jul. 12, 2010, which designates the US and claims priority to Swedish Application Nos. 0900981-2; 0900957-2, 0900959-8, 0900960-6, 0900962-2; 0900963-0; 0900965-5; 0900966-3; 0900968-9; 0900969-7; 0900970-5; 0900972-1; 0900973-9; 0900974-7; 0900976-2; 0900978-8 and 0900958-0, all filed Jul. 10, 2009, and which claims the benefit of U.S. Provisional Nos. 61/229,738; 61/229,739; 61/229,743; 61/229,745; 61/229,746; 61/229,747; 61/229,748; 61/229,751; 61/229,752; 61/229,755; 61/229,761; 61/229,767; 61/229,778; 61/229,786; 61/229,789; 61/229,796 and 61/229,735 all filed on Jul. 30, 2009, respectively, the entire contents of each of which are hereby incorporated by reference.

TECHNICAL FIELD

The invention relates generally to hip joint prosthesis.

BACKGROUND

Hip joint Osteoarthritis is a syndrome in which low-grade inflammation results in pain in the hip joints, caused by abnormal wearing of the Cartilage that acts as a cushion inside if the hip joint. This abnormal wearing of the cartilage also results in a decrease of the joints lubricating fluid called Synovial fluid. Hip joint Osteoarthritis is estimated to affect 80% of all people over 65 years of age, in more or less serious forms.

The present treatment for hip osteoarthritis comprises NSAID drugs, local injections of Hyaluronic acid or Glucocorticoid to help lubricating the hip joint, and replacing parts of the hip joint with a prosthesis through hip joint surgery.

The replacing of parts of the hip joint is one of the most common surgeries to date performed at hundreds of thousands of patients in the world every year. The most common method comprises placing a metal prosthesis in Femur and a plastic bowl in Acetabulum. This operation is done through an incision in the hip and upper thigh and through Fascia Lata and the lateral muscles of the thigh. To get access to the joint, the supporting Fibrous Capsule attached to Femur and Ilium needs to be penetrated, making it difficult to get a fully functional joint after the surgery. Femur is then cut at the neck with a bone saw and the prosthesis is placed in femur either with bone cement or without. Acetabulum is slightly enlarged using an Acetabular reamer, and the plastic bowl is positioned using screws or bone cement.

The complications after hip joint surgery includes dislocation of the hip joint and loosening of the prosthesis from its fixation in the femoral bone. The loosening and/or dislocation of the prosthesis could be induced by an abnormal strain being placed on the hip joint from e.g. the patient falling or making a rapid movement of the hip. A completely fixed hip joint prosthesis, without the possibility to dislocate would increase the risk of the prosthesis loosening from its fixation in the femoral bone, since the entire strain is then placed on the femoral bone.

A hip joint prosthesis that could reduce the complications after hip joint surgery would therefore be desirable.

SUMMARY

A medical device for implantation in a hip joint of a patient is provided. The medical device comprises a first piece adapted to be fixated to the pelvic bone. The first piece comprises a convex contacting surface adapted to be partially placed inside a concave contacting surface. The medical device further comprises a second piece adapted to be fixated to the femoral bone. The second piece comprises a concave contacting surface adapted to partially surround the convex contacting surface of said first piece, when implanted. The medical device further comprises a releasing member adapted to, in a first state, hold the first piece attached to the second piece, and in a second state release the first piece from the second piece. The releasing member is adapted to change from the first state to the second state when a pre-determined strain is placed on the releasing member. The construction with a releasing member reduces the risk of damaging any structures of the human body and/or interconnections between the human body and prosthetic parts.

According to one embodiment of the medical device, the convex contacting surface of the first and/or second piece is at least partially spherical.

According to another embodiment the concave contacting surface of the second piece is at least partially spherical.

The first piece could according to one embodiment comprise a ball shaped piece, and the second piece could comprise a bowl shaped piece. The ball shaped piece could be adapted to be placed in the bowl shaped piece to replace a functioning hip joint. The ball shaped piece could be adapted to be fixated in the bowl shaped piece using the releasing member.

The releasing member according to any of the embodiments herein could be adapted to non-invasively change from the first state to the second state and from the second state to the first state, when a pre-determined strain is placed on the releasing member.

At least one of the first and second pieces comprises at least two parts adapted to be in contact with each other when the medical device is implanted in the patient.

According to another embodiment the first or said second pieces are adapted to be introduced through a hole in the pelvic bone of the patient. One of said at least two pieces could be adapted to be mechanically fixated to each other after the at least two pieces have been introduced into the hip joint through a hole in the pelvic bone of the patient.

The hole in the pelvic bone could have a cross sectional area smaller than 530 mm2, smaller than 380 mm2, smaller than 250 mm2, smaller than 180 mm2 or smaller than 110 mm2.

According to one embodiment, the second piece of the medical device comprises the releasing member according to any of the embodiments herein. The releasing member could comprise an elastic portion, which for example could comprise an elastic material, a spring or an elastic band. The elastic band could be adapted to at least partly encircle said ball shaped piece.

According to another embodiment of the medical device, the releasing member comprises at least one of bendable portion, a flexible portion, a compressible portion, a movable portion or a movable part.

According to yet another embodiment the releasing member comprises a magnet adapted to hold the first piece to the second piece.

According to yet another embodiment the releasing member comprises a rupture device adapted to fail at a pre-determined strain. The rupture device could for example comprise a rupture band and/or a rupture pin.

The releasing member could according to one embodiment comprise multiple holding members, which in turn could be adapted to slide against the first piece, or roll against the first piece. According to one embodiment the holding member adapted to roll comprises a ball shaped holding member.

The first piece of the medical device according to any one of the embodiments herein could comprise at least two parts adapted to be in contact with each other when the medical device is implanted in the patient. One of the at least two parts could be adapted to be mechanically fixated to the second of the at least two parts after the at least two parts have been introduced into the hip joint through a hole in the pelvic bone of the patient.

The first piece could according to one embodiment comprise a flexible portion or an elastic portion adapted to enable the medical device to be inserted through a hole in the pelvic bone, the elastic portion enabling the compression of the first piece in at least one direction.

According to yet another embodiment the first piece comprises a first area and a second area. The first area comprises a first material adapted to be elastic and the second area comprises a second material adapted to be elastic. The first material could be adapted to be more elastic than the second material.

According to one embodiment of the medical device the second piece comprises at least two parts adapted to be in contact with each other when the medical device is implanted in the patient. One of the at least two parts could be adapted to be mechanically fixated to a second of the at least two parts after the at least two parts have been introduced into the hip joint through a hole in the pelvic bone of the patient.

The medical device could according to yet another embodiment comprise a calibration member for calibrating the pre-determined strain required for the releasing member to change from the first state to said second state. The calibration member could be a calibration screw.

A method of installing a medical device according to any of the embodiments herein is further provided. The method comprises the steps of: exposing the hip joint through a surgical or arthroscopic procedure, fixating the first piece of the medical device to the pelvic bone, fixating the second piece of the medical device to the femoral bone, placing the first piece in connection with the second piece, and holding the first piece to the second piece using the releasing member.

According to one embodiment the step of holding the first piece to the second piece using the releasing member comprises holding the first piece to the second piece using an elastic member. According to yet another embodiment the step of holding the first piece to the second piece using the elastic member, comprises holding the first piece to the second piece using an elastic band.

According to one embodiment the step of holding the first piece to the second piece using the releasing member could comprise holding the first piece to the second piece using a rupturing member. The rupturing member could be a rupturing band.

According to other embodiment the step of holding the first piece to the second piece comprises holding the first piece to the second piece using a spring loaded member.

A medical device for implantation in a hip joint of a patient is further provided. The medical device comprises a first and second piece and a releasing member adapted to, in a first state hold the first piece attached to the second piece, and in a second state release the first piece from the second piece. The releasing member is adapted to change from the first state to the second state when a pre-determined strain is placed on the releasing member.

According to one embodiment the first piece comprises a ball shaped piece, adapted to replace at least the surface of the caput femur in the hip joint.

According to one embodiment the second piece comprises a bowl shaped piece, adapted to replace at least the acetabulum surface in the hip joint.

According to another embodiment the first piece comprises a ball shaped piece and the second piece comprises a bowl shaped piece, and the ball shaped piece is adapted to be placed in the bowl shaped piece to replace a functioning hip joint, thereby creating an entirely artificial hip joint. The ball shaped piece could be adapted to be fixated in the bowl shaped piece using the releasing member.

The releasing member according to any of the embodiments could be adapted to non-invasively change from the first state to the second state and from the second state to the first state, when a pre-determined strain is placed on said releasing member. Thereby, if dislocated the hip joint can be reinstated without the need of a surgical procedure.

The at least one of the first and second piece could comprise at least two parts adapted to be in contact with each other when the medical device is implanted in the patient.

The first and/or the second piece could be adapted to be introduced through a hole in the pelvic bone of the patient.

According to one embodiment the at least two pieces are adapted to be mechanically fixated to each other after the at least two pieces have been introduced into the hip joint through a hole in the pelvic bone of the patient.

Releasing Member

According to one embodiment the first piece of the medical device comprises the releasing member. Which could be a ball shaped piece of the medical device comprising the releasing member. According to another embodiment the second piece of the medical device comprises the releasing member. Which could be a bowl shaped piece of the medical device comprising the releasing member.

According to another embodiment the releasing member comprises an elastic portion, which in turn could comprise an elastic material.

According to yet another embodiment the releasing member comprises a bendable and/or flexible and/or compressible portion. It is furthermore conceivable that the releasing member comprises a movable portion or movable part.

In the embodiments where the medical device comprises an elastic portion, the elastic portion could comprise a spring and/or an elastic band, which could be adapted to at least partly encircle the ball shaped piece and thereby holding the ball shaped piece in the bowl shaped piece. The elastic band could further be adapted to be placed between the ball shaped piece and the bowl shaped piece.

According to yet another embodiment the releasing member comprises a magnet adapted to hold the first piece to the second piece.

According to another embodiment the releasing member comprises a rupture device adapted to fail at a pre-determined strain, for releasing the first piece from the second piece. The rupture device could comprise a rupture band, which could be adapted to at least partly encircle the ball shaped piece. The rupture band could, according to one embodiment be placed between the ball shaped piece and the bowl shaped piece, and could comprise a rupture pin.

The releasing member could comprise multiple holding members, and the holding members or holding member could be adapted to slide against said first piece and/or adapted to roll against said first piece. The holding member could comprise a ball shaped holding member.

First Piece

According to one embodiment, the first piece comprises at least two parts adapted to be in contact with each other when the medical device is implanted in the patient.

The first piece, according to any of the embodiments, could be adapted to be introduced through a hole in the pelvic bone of the patient.

According to one embodiment, one of the at least two parts is adapted to be mechanically fixated to the second of the at least two parts after the at least two parts have been introduced into the hip joint through a hole in the pelvic bone of the patient.

The first piece could comprise a flexible portion and/or an elastic portion adapted to enable the medical device to be inserted through a hole in the pelvic bone. The elastic portion could enable the compression of the first piece in at least one direction.

The first piece could comprise a first area and a second area, the first area could comprise a first material adapted to be elastic and the second area could comprise a second material adapted to be elastic, and the first material could be adapted to be more elastic than the second material.

Second Piece

According to one embodiment the second piece comprises at least two parts adapted to be in contact with each other when the medical device is implanted in the patient. The second piece could be adapted to be introduced through a hole in the pelvic bone of the patient.

According to another embodiment, one of said at least two parts could be adapted to be mechanically fixated to a second of the at least two parts after the at least two parts have been introduced into the hip joint through a hole in the pelvic bone of the patient.

According to yet another embodiment the medical device comprises at least a three-dimensionally curved hip joint surface comprising: an inner surface, and an outer surface. The inner surface comprises six different points: a first point, a second point, a third point, a fourth point, a fifth point, and a sixth point, all points located on different places along a length axis of the inner surface. A first straight line, reaching from said first point to said second point is parallel to a second straight line reaching from said third point to said fourth point, which in turn is parallel to a third straight line reaching from said fifth point to said sixth point. Furthermore, the first and third straight lines are shorter than said second straight line, and said second straight line is positioned between said first and said third straight lines.

The medical device could further comprise a calibration member for calibrating the pre-determined strain required for said releasing member to change from said first state to said second state. The calibration member could be a calibration screw.

The normal hip joint have a collum femur, having an axial distribution leading to a caput femur, having a substantially ball shaped configuration with a maximum diameter substantially perpendicular to the centre axis of the prolongation of said axial distribution of said collum femur. The caput femur is placed in a bowl shaped acetabulum creating the hip joint. The bowl shaped acetabulum have an opening and a second axial distribution with a center axis from the center of the bottom of the acetabulum bowl and following the center of the bowl towards the opening and caput femur, wherein the acetabulum have a maximum diameter substantially perpendicular to the center axis of the second axial distribution of the acetabulum. The prolongation of the centre axis of the axial distribution is identical to the center axis of the second axial distribution, when the caput femur is in a centered and symmetrical position in the acetabulum bowl. The medical device comprises two artificial hip joint surfaces, the first piece comprises; the artificial hip joint surface comprising, an artificial caput femur surface adapted to at least partly replace and replacing the joint surface of the caput femur, on the opposite side of collum femur, and adapted to, when mounted in the joint, be placed in the acetabulum bowl or an artificial replacement therefore. The artificial caput femur surface, comprising at least one first beyond part of the surface adapted to cover and/or going into the bone of said caput femur on at least a part of said caput femur beyond the maximum diameter of said caput femur, away from said acetabulum bowl towards said collum femur, when mounted on said caput femur in its functional position in the joint. The at least one first beyond part is adapted to have a closest perpendicular distance to said center axis, being smaller than the distance between the periphery of said maximum diameter of said caput femur and said center axis, thus adapted to create and creating a more stable position of said artificial caput femur surface when mounted on said caput femur in said functional position. The beyond part comprises at least a part of the releasing member.

The normal hip have a collum femur having an axial distribution leading to a caput femur having a substantially ball shaped configuration with a maximum diameter substantially perpendicular to the centre axis of the prolongation of said axial distribution of said collum femur. The caput femur is placed in a bowl shaped acetabulum creating the hip joint. The bowl shaped acetabulum have an opening and a second axial distribution with a center axis from the center of the bottom of said acetabulum bowl and following the center of said bowl towards the opening and caput femur. The acetabulum have a maximum diameter substantially perpendicular to the center axis of said second axial distribution of the acetabulum, the prolongation of the center axis of the axial distribution is identical to the center axis of the second axial distribution, when the caput femur is in a centered and symmetrical position in the acetabulum bowl. The medical device comprises two artificial hip joint surfaces, the artificial hip joint surface comprising, an artificial acetabulum surface adapted to at least partly replace and replacing the joint surface of the acetabulum, and adapted to be placed onto the caput femur, or an artificial replacement therefore, when mounted in the hip joint. The artificial acetabulum surface, comprises at least one first beyond part of the surface adapted to cover at least a part of the caput femur or the artificial replacement therefore beyond the maximum diameter of the acetabulum, away from the acetabulum bowl towards the collum femur, when mounted onto the caput femur or an artificial replacement therefore, in its functional position in the hip joint. The at least one first beyond part adapted to have a closest perpendicular distance to said centre axis, being smaller than the distance between the periphery of said maximum diameter of said artificial acetabulum surface and said centre axis, thus adapted to create and creating a more stable position of the artificial acetabulum surface when mounted on the caput femur or an artificial replacement therefore, in said functional position in said hip joint. The first beyond part comprises the releasing member.

The releasing member, according to any of the embodiments could comprise an elastic portion and/or a bendable portion and/or a flexible portion and/or a compressible portion and/or a movable portion and/or a movable part, for enabling the releasing of the first piece from the second piece.

A method of installing a medical device according to any of the embodiments is further provided, the method comprises the steps of: exposing the hip joint through a surgical or arthroscopic procedure, fixating said first piece of said medical device to the femoral bone, fixating said second piece of said medical device to the pelvic bone, placing said first piece in connection with said second piece, and holding said first piece to said second piece using said releasing member.

According to one embodiment, the step of holding the first piece to the second piece comprises holding the first piece to the second piece using an elastic member.

According to one embodiment, the step of holding the first piece to the second piece comprises holding the first piece to the second piece using a rupturing member.

According to one embodiment, the step of holding the first piece to the second piece comprises holding the first piece to the second piece using a spring loaded member.

According to one embodiment, the step of holding the first piece to the second piece comprises holding the first piece to the second piece using an elastic band.

According to one embodiment, the step of holding the first piece to the second piece comprises holding the first piece to the second piece using a rupturing band.

Please note that any embodiment or part of embodiment, feature, method, associated system, part of system described herein or in the associated figures may be combined in any way.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is now described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 shows the hip joint in section.

FIG. 2 shows the first step in a conventional hip joint surgery,

FIG. 3 shows the step of removing the caput femur from the hip joint capsule,

FIG. 4 shows the incisions made in a laparoscopic/arthroscopic method,

FIG. 5 shows the instruments used in a laparoscopic/arthroscopic method,

FIG. 6 shows the step of creating a hole in the pelvic bone of a patient,

FIG. 7 shows details of a laparoscopic operation,

FIG. 8 shows the patient in section when a laparoscopic operation is performed,

FIG. 9 shows the hip joint in section when a medical device has been provided, in a first state,

FIG. 10 shows the hip joint in section when a medical device has been provided, in a second state,

FIG. 11 shows the hip joint in section when a medical device has been provided, in a first state,

FIG. 12 shows the hip joint in section when a medical device has been provided, in a second state,

FIG. 13 shows the medical device in section,

FIG. 14 shows an alternative embodiment of the medical device shown in FIG. 11, in a first state,

FIG. 15 shows an alternative embodiment of the medical device shown in FIG. 11, in a second state,

FIG. 16 shows the hip joint in section, when a medical device according to yet another embodiment is provided, in a first state,

FIG. 17 shows the hip joint in section, when a medical device according to yet another embodiment is provided, in a second state,

FIG. 18a shows the hip joint in section when a medical device comprising an elastic or rupture band has been provided, in a first state,

FIG. 18b shows the medical device of FIG. 18a , in section, in a first state,

FIG. 19a shows the hip joint in section when a medical device comprising an elastic or rupture band is provided, in a second state,

FIG. 19b shows the medical device of FIG. 19a , in section, in a second state,

FIG. 20 shows the hip joint in section, when a medical device according to yet another embodiment has been provided, in a first state,

FIG. 21 shows the hip joint in section, when a medical device according to yet another embodiment has been provided, in a second state,

FIG. 22 shows the hip joint in section, when a medical device comprising a rupture band has been provided, in a first state,

FIG. 23 shows the hip joint in section, when a medical device comprising a rupture band has been provided, in a second state,

FIG. 24 shows the hip joint in section, when a medical device according to yet another embodiment has been provided, in a first state,

FIG. 25 shows the hip joint in section, when a medical device according to yet another embodiment has been provided, in a second state,

FIG. 26 shows the hip joint in section when a medical device, according to an embodiment where the artificial acetabulum surface comprises elastic elements, has been provided, in a first state,

FIG. 27 shows the hip joint in section when a medical device, according to an embodiment where the artificial acetabulum surface comprises elastic elements, has been provided, in a second state,

FIG. 28 shows an alternative embodiment of the medical device shown in FIG. 26,

FIG. 29a shows the hip joint in section when a medical device adapted to hold the caput femur 5, or an artificial replacement therefore, to the artificial acetabulum by means of magnetic force, has been provided, in a first state,

FIG. 29b shows the hip joint in section when a medical device adapted to hold the caput femur 5, or an artificial replacement therefore, to the artificial acetabulum by means of magnetic force, has been provided, in a second state,

FIG. 30a shows the medical device according to another embodiment, in a first state, in which the medical device comprises a prosthetic part fixated in the femoral bone,

FIG. 30b shows the medical device according to the embodiment in FIG. 30a when a breakpin has failed,

FIGS. 30c and 30d shows the replacement of a failed breakpin by removal of the pieces of the failed breakpin.

FIG. 31 shows, schematically, the artificial acetabulum or artificial caput femur,

FIG. 32a shows the artificial acetabulum or artificial caput femur, in section,

FIG. 32b shows another embodiment of a medical device,

FIG. 32c shows the medical device according to an embodiment where the releasing member comprises an elastic wing.

FIG. 32d shows the medical device when in its second state, in which the releasing member releases the caput femur or an artificial replacement therefore,

FIG. 33 shows the principle of an alternative embodiment,

FIG. 34 shows the principle of an alternative embodiment,

FIG. 35 shows the principle of an alternative embodiment,

FIG. 36a shows an embodiment of the locking/releasing member,

FIG. 36b shows the hip joint in section in an embodiment when the locking/releasing member locks an artificial caput femur in artificial acetabulum.

FIG. 36c shows the hip joint in section in an embodiment when the locking/releasing member releases the artificial caput femur from the artificial acetabulum.

FIG. 36d shows another embodiment of the locking/releasing member,

FIG. 36e shows the hip joint in section in an embodiment when the locking/releasing member according to the embodiment of FIG. 36d locks the artificial caput femur to the artificial acetabulum.

FIG. 36f shows the hip joint in section in an embodiment when the locking/releasing member according to the embodiment of FIG. 36d releases the artificial caput femur from the artificial acetabulum.

FIG. 36g shows another embodiment of the locking/releasing member,

FIG. 36h shows another embodiment of the locking/releasing member,

FIG. 36i shows the hip joint in section when an artificial hip joint is being assembled,

FIG. 36j shows the hip joint in section when an artificial hip joint is being assembled,

FIG. 36k shows the hip joint in section when an artificial hip joint is assembled,

FIG. 36m shows the hip joint in section when an artificial hip joint is in its releasing state.

DETAILED DESCRIPTION

Elasticity is to be understood as a materials ability to deform in an elastic way.

Elastic deformation is when a material deforms under stress (e.g. external forces), but returns to its original shape when the stress is removed. A more elastic material is to be understood as a material having a lower modulus of elasticity. The elastic modulus of an object is defined as the slope of its stress-strain curve in the elastic deformation region. The elastic modulus is calculated as stress/strain, where stress is the force causing the deformation, divided by the area to which the force is applied; and strain is the ratio of the change caused by the stress.

Stiffness is to be understood as the resistance of an elastic body to deformation by an applied force.

Functional hip movements are to be understood as movements of the hip that at least partly correspond to the natural movements of the hip. On some occasions the natural movements of the hip joint might be somewhat limited or altered after hip joint surgery, which makes the functional hip movements of a hip joint with artificial surfaces somewhat different than the functional hip movements of a natural hip joint.

The functional position of an implantable medical device or prosthesis is the position in which the hip joint can perform functional hip movements. The final position is to be understood as a functional position in which the medical device needs no further position change.

Biocompatible material is to be understood as being a material with low level of immune response. Biocompatible materials are sometimes also referred to as biomaterials. Analogous is biocompatible metals a biocompatible metal with low immune response such as titanium or tantalum. The biocompatible metal could also be a biocompatible alloy comprising at least one biocompatible metal.

Form fitting is to be understood as an element having a part or section which is adapted to enable a mechanical connection of said element to at least one other element using said part or section. Form fitted structure is a structure of an element which enables form fitting.

The medical device according to any of the embodiments could comprise at least one material selected from a group consisting of: polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA) and fluorinated ethylene propylene (FEP). It is furthermore conceivable that the material comprises a metal alloy, such as cobalt-chromium-molybdenum or titanium or stainless steel, or polyethylene, such as cross-linked polyethylene or gas sterilized polyethylene. The use of ceramic material is also conceivable, in the contacting surfaces or the entire medical device such as zirconium or zirconium dioxide ceramics or alumina ceramics. The part of the medical device in contact with human bone for fixation of the medical device to human bone could comprise a poorhouse structure which could be a porous micro or nano-structure adapted to promote the growth-in of human bone in the medical device for fixating the medical device. The porous structure could be achieved by applying a hydroxy-apatite (HA) coating, or a rough open-pored titanium coating, which could be produced by air plasma spraying, a combination comprising a rough open-pored titanium coating and a HA top layer is also conceivable. The contacting parts could be made of a self lubricated material such as a waxy polymer, such as PTFE, PFA, FEP, PE and UHMWPE, or a powder metallurgy material which could be infused with a lubricant, which preferably is a biocompatible lubricant such as a Hyaluronic acid derivate. It is also conceivable that the material of contacting parts or surfaces of the medical device herein is adapted to be constantly or intermittently lubricated. According to some embodiments the parts or portions of the medical device could comprise a combination of metal materials and/or carbon fibers and/or boron, a combination of metal and plastic materials, a combination of metal and carbon based material, a combination of carbon and plastic based material, a combination of flexible and stiff materials, a combination of elastic and less elastic materials, Corian or acrylic polymers.

In the following a detailed description of preferred embodiments of the present invention will be given. In the drawing figures, like reference numerals designate identical or corresponding elements throughout the several figures. It will be appreciated that these figures are for illustration only and are not in any way restricting the scope of the invention. Thus, any references to direction, such as “up” or “down”, are only referring to the directions shown in the figures. Also, any dimensions etc. shown in the figures are for illustration purposes.

FIG. 1 shows the hip joint of a human patient in section. The hip joint comprises a caput femur 5, or an artificial replacement therefore, placed at the very top of collum femur 6 which is the top part of the femoral bone 7. The caput femur 5, is in connection with the acetabulum 8 which is a bowl shaped part of the pelvic bone 9. Both the caput femur surface 10 and the acetabulum surface 11 is covered with articular cartilage 13 which acts as a cushion in the hip joint. In patients with hip joint osteoarthritis, this articular cartilage 13 is abnormally worn down due to a low grade inflammation. The hip joint is surrounded by the hip joint capsule 12 which provides support for the joint and hinders luxation. After conventional hip joint surgery, penetrating the hip joint capsule 12, the capsule 12 is dramatically weakened due to the limited healing possibilities of its ligament tissue. By performing hip joint surgery without damaging the hip joint capsule 12 the patient can fully recover and place equal amount of strain on an artificial joint as is possible on a natural one.

FIG. 2 shows a lateral view of a conventional hip joint surgery where an incision 112 is made in the thigh 113 enabling the surgeon to reach the femoral bone 7 on which the caput femur 5 is located. The femoral bone 7 is then extracted from the hip joint capsule 12 exposing the caput femur 5, which is replaced or resurfaced during the operation.

FIG. 3 shows the placing of an artificial caput femur surface 45 on the caput femur 5 in conventional surgery. However according to other embodiments of the state of the art the entire collum femur 6 is removed using a bone saw, after which a prosthetic part comprising the caput femur is fixated in the femoral bone using bone cement or mechanical fixating members. A bowl shaped cup is then placed in the acetabulum 8 to act as the contacting surface against the new artificial caput femur 45 when the hip joint is performing functional hip movements in its functional position. According to prior art, the artificial caput femur surface and the artificial acetabulum surface is being kept together by means of the hip joint capsule, which is dramatically weakened when the capsule has been penetrated during an operation.

An alternative way of operating a hip joint will now be described.

FIG. 4 shows a frontal view of the body of a human patient. A laparoscopic/arthroscopic method of operating the hip joint, from the opposite side from acetabulum, is according to a first embodiment performed starting with making small incisions 14 in the abdominal wall of the human patient. The small incisions enable the surgeon to insert laparoscopic trocars into the abdomen of the human patient. According to the first embodiment the incisions 14 passes through the rectus abdominis and peritoneum in to the abdomen of the human patent. According to a second preferred embodiment the small incisions 15 is conducted through the rectus abdominis and in to the pelvic area, below peritoneum. According to a third embodiment the small incisions 16 is performed just between Ilium and the surrounding tissue, an incision 16 which could enable the pelvic bone to be dissected with very little penetration of fascia and muscular tissue. According to a fourth embodiment the incision 17 is made in the inguinal channel. In all of the four embodiments the tissue surrounding the pelvic bone 9 in the area opposite to acetabulum 8 is removed or penetrated which enables the surgeon to reach the pelvic bone 9.

It is obvious that the methods described may both be combined or altered reaching the same goal to dissect the pelvic bone on the opposite side of the acetabulum.

After dissecting the pelvic bone 9 a hole 18 is created in the bone 9, as shown in FIG. 6. The hole 18 passes through the pelvic bone from the opposite side from acetabulum 8 and into the hip joint 19. The medical, according to any one the embodiments herein could be adapted to be inserted through the hole 18 in the pelvic bone 9. For this purpose the medical device could comprise a first and second piece adapted to be introduced through the hole 9 and thereafter be mounted and mechanically fixated to each other in situ for creating a mounted medical device. This is further explained with reference to FIGS. 36h and 36 i.

The medical device, or the first and second piece of the medical device could be adapted to be introduced through a hole 18 in the pelvic bone 9, having a cross sectional area smaller than 530 m2 or hole 18 in the pelvic bone 9 having a cross sectional area smaller than 380 mm2, or a hole 18 in the pelvic bone 9 having a cross sectional area smaller than 250 mm2, or a hole in the pelvic bone having a cross sectional area smaller than 180 mm2, or a hole 18 in the pelvic bone 9 having a cross sectional area smaller than 110 mm2. A smaller hole creates a less invasive procedure in which it is further conceivable that the medical device needs to be mounted from more than two pieces. In some embodiments the medical device is mounded from several pieces adapted to be mechanically connected to a base piece.

FIG. 5 shows a frontal view of the body of a human patient, illustrating the laparoscopic method of operating the hip joint from the opposite side from acetabulum 8. The hip joint comprises the acetabulum 8 and the caput femur 5. The small incisions 14 in the abdominal wall of the human patient allows the insertion of laparoscopic trocars 33 a,b,c into the body of the patients. Whereafter one or more camera 34, a surgical instrument adapted to create a hole in the pelvic bone 35, or instruments 36 for introducing, placing, connecting, attaching, creating or filling prosthesis or prosthetic parts, can be inserted into said body through said laparoscopic trocars 33 a,b,c.

FIG. 6 shows the creation of a hole 18 in the pelvic bone 9 from the abdominal side of acetabulum using a bone contacting organ 22.

FIG. 7 shows a close-up of the insertion 37 of prosthetic parts 38 into the patient's body through said laparoscopic trocars 33 a,b,c. The prosthetic parts could be parts of the artificial caput femur 45, the artificial acetabulum 65 or prosthetic parts or bone material adapted to be used to close the hole 18 created in the pelvic bone 9.

FIG. 8 shows a lateral view of the body of a human patient, with the hip joint shown in section. The hip joint comprises a caput femur 5 placed at the very top of collum femur 6 which is the top part of the femur bone 7. The caput femur 5 is in connection with the acetabulum 8 which is a bowl shaped part of the pelvic bone 9. Laparoscopic trocars 33 a,b,c is being used to reach the hip joint 39 with one or more camera 34, a surgical instrument 35 adapted to create a hole in the pelvic bone 9, or instruments 36 for introducing, placing, connecting, attaching, creating or filling prosthesis or prosthetic parts.

FIG. 9 shows an artificial bowl shaped acetabulum cup 65 placed in the pelvic bone 9. The artificial bowl shaped acetabulum cup 65 comprises releasing members 801 adapted, in a first state, to hold the caput femur 5 which is a ball shaped piece attached to the collum femur 6 in position in the hip joint to the artificial bowl shaped acetabulum cup 65 placed in the pelvic bone 9. In a second state the releasing member 801 is adapted to release the caput femur 5, or an artificial replacement therefore, from the artificial bowl shaped acetabulum cup 65 placed in the pelvic bone 9. The releasing member 801 is adapted to change from the first state to the second state when a pre-determined strain is placed on the releasing member 801. The strain preferably being caused by an abnormal movement of the hip joint, e.g. as the result of the patient falling. According to the embodiment shown in FIG. 9 the releasing member 801 comprises an elastic portion comprising elastic material, in the embodiment shown being the entire releasing member 801. The releasing member is adapted to non-invasively be able to change from the first state to the second state and from the second state to the first state, when a pre-determined strain is placed on the releasing member 801.

FIG. 10 shows the hip joint in section when the releasing member 801 is in its second state, wherein the releasing member 801 is adapted to release the caput femur 5, or an artificial replacement therefore, from the artificial bowl shaped acetabulum cup 65 placed in the pelvic bone 9. The releasing member 801 has changed from the first state to the second state because of a pre-determined strain has been placed on the releasing members 801.

FIG. 11 shows the medical device according to an embodiment where the artificial bowl shaped acetabulum surface 65 comprises releasing members 801 comprising holding members 802 a,b adapted to slide against the caput femur 5, or an artificial replacement therefore. The holding members are adapted to, in a first state, hold the caput femur 5, or an artificial replacement therefore, which is a ball shaped part attached to the collum femur 6 in position in the hip joint to the artificial bowl shaped acetabulum cup 65 placed in the pelvic bone 9. In a second state the releasing member 801 is adapted to release the caput femur 5, or an artificial replacement therefore, from the artificial bowl shaped acetabulum cup 65 placed in the pelvic bone 9. The holding members 802 a,b are spring loaded through a spring 803 a,b being placed between a calibration member, being a calibration screw 804 a,b, and the holding members 802 a,b. The force exerted on the holding members 802 a,b from the spring 803 a,b is adapted to hold the caput femur 5, or an artificial replacement therefore, in the artificial acetabulum 65 in normal, functional hip joint movements, but release the caput femur 5, or an artificial replacement therefore, from the artificial acetabulum 65 when a pre-determined strain is placed on the releasing member preferably being caused by an abnormal movement of the hip joint, e.g. as the result of the patient falling. The calibration screws 804 a,b enables the pre-determination of the strain which will cause the holding members 802 a,b to change from being in a first state to being in a second state.

FIG. 12 shows the releasing members in their second state, when a pre-determined strain has been exceeded, preferably being caused by an abnormal movement of the hip joint, e.g. as the result of the patient falling. The holding members 802 a,b are retracted into sleeves 806 of the artificial acetabulum surface 65, thereby compressing the springs 803 a,b. The retraction of the holding members 802 a,b causes the caput femur 5, or an artificial replacement therefore, to be dislocated/luxated from its position in the artificial acetabulum surface 65, which, when large strain is placed on the hip joint and femoral bone 7, reduces the risk of the patient fracturing the femoral bone 7 or the pelvic bone 9. The holding members 802 a,b are adapted to non-invasively be able to change from the first state to the second state and from the second state to the first state, when a pre-determined strain is placed on the holding members 802 a,b.

FIG. 13 shows the artificial acetabulum 65 in section with the holding members 802, placed in sleeves 806 evenly distributed along the cross-section of the artificial acetabulum 65, holding the caput femur 5, or an artificial replacement therefore, in position in the artificial acetabulum 65.

FIG. 14 shows an alternative embodiment of the principle shown in FIGS. 11-13, wherein the holding members 802 a,b, comprises ball shaped members 805 a,b in contact with the caput femur 5, or an artificial replacement therefore, ant being adapted to roll against the caput femur 5, or an artificial replacement therefore, holding the caput femur 5, or an artificial replacement therefore, in place in the artificial acetabulum 65 by the holding members 802 a,b exerting force on the caput femur 5, or an artificial replacement therefore, through the contact with the springs 803 a,b supported by the calibration screws 804 a,b.

FIG. 15 shows the releasing members in their second state, when a pre-determined strain has been exceeded, preferably being caused by an abnormal movement of the hip joint, e.g. as the result of the patient falling. The holding members 802 a,b, comprising the ball shaped members 805 a,b, are retracted into sleeves 806 of the artificial acetabulum surface 65, thereby compressing the springs 803 a,b. The retraction of the holding members 802 a,b causes the caput femur 5, or an artificial replacement therefore, to be dislocated/luxated from its position in the artificial acetabulum surface 65, which, when large strain is placed on the hip joint and femoral bone 7, reduces the risk of the patient fracturing the femoral bone 7 or the pelvic bone 9. The holding members 802 a,b are adapted to non-invasively be able to change from the first state to the second state and from the second state to the first state, when a pre-determined strain is placed on the holding members 802 a,b, which enables the caput femur 5, or an artificial replacement therefore, to be replaced in the artificial acetabulum 65 without a surgical procedure.

FIG. 16 shows the medical device in an embodiment wherein the releasing members 801 comprises a rupture device 807, 808, 809 adapted to fail at a pre-determined strain. According to this embodiment the rupture device is a rupture pin 807, 808, 809 comprising a base part 809 a,b fixated to the artificial acetabulum 65 and a rupture part 807 a,b attached to the base part 809 a,b through a weakened section 808 a,b, in which section the rupture part 807 a,b is detached from the base part 809 a,b when a predetermined strain is placed on the rupture device in contact with the caput femur 5, or an artificial replacement therefor.

FIG. 17 shows the medical device according to the embodiment of FIG. 16 when the rupture device has failed due to a pre-determined strain on the rupture device being exceeded. According to one embodiment, (not shown) the rupture parts 807 a,b are secured to the base part through a security wire keeping rupture parts 807 a,b in proximity to the base part 809 a,b even after the failure of the rupture device.

FIG. 18a shows the medical device according to an embodiment where the artificial acetabulum 65 comprises a circular sleeve 806, in which an elastic or rupture band 810 is provided. The elastic or rupture band 810 is adapted to at least partly encircle the ball shaped caput femur 5, or artificial replacement therefore. When a pre-determined strain is placed on the elastic or rupture band 810 the circular opening encircling the caput femur 5, or an artificial replacement therefore, is expanded and the caput femur 5, or an artificial replacement therefore, is released from the artificial acetabulum 65, to which it is held by means of the elastic band 810. In embodiments where the medical device comprises a rupture band 810 holding the caput femur 5, or an artificial replacement therefore, in the artificial acetabulum 65, a weakened portion 811 of the band 810 fails and thus the circular opening encircling the caput femur 5, or an artificial replacement therefore, is expanded and the caput femur 5, or an artificial replacement therefore, is released from the artificial acetabulum 65. In the embodiments where the band 810 is an elastic band 810 it is conceivable that the band 810 comprises an elastic part or section, or that the entire band 810 is made of an elastic material.

FIG. 18 b shows the medical device in section when the elastic or rupturing band 810, holding the caput femur 5, or an artificial replacement therefore, is placed in a circular sleeve 806 in the artificial acetabulum 65. An opening or weakened portion 811 is provided perpendicular to the circumference of the band 810.

FIG. 19a shows the medical device in a second state where the caput femur 5, or an artificial replacement therefore, is released from the connection with the acetabulum, after a pre-determined stain has been placed on the elastic or rupture band 810. As shown in FIG. 19b the gap or weakened part has been expanded, thereby allowing the caput femur, or an artificial replacement therefore, 5 to pass through the opening defined by the elastic or rupture band 810. The medical device could be adapted to non-invasively be able to change from the first state to the second state and from the second state to the first state, when a pre-determined strain is placed on the band 810, which enables the caput femur 5, or an artificial replacement therefore, to be replaced in the artificial acetabulum 65 without a surgical procedure.

FIG. 20 shows the medical device according to an embodiment where the releasing member 801 comprises an elastic wing of the artificial acetabulum 65, which is assisted by an elastic or rupture band 810 encircling the medical device by enclosing the caput femur 5, or an artificial replacement therefore, in the artificial acetabulum 65 passing beyond the point of the caput femur 5, or an artificial replacement therefore, having a largest cross-sectional distance. The elastic or rupture band 810 is held in place to the artificial acetabulum 65 by means of the band 810 being placed in a groove along the circumference of the artificial acetabulum 65. However, said groove could be assisted or replaced by an adhesive or a mechanical fixation element.

FIG. 21 shows the medical device when in its second state, in which the releasing member 801 releases the caput femur 5, or an artificial replacement therefore, from the artificial acetabulum 65. In embodiments when the band 810 is an elastic band 810 it is expanded, thereby enlarging the hole through which the caput femur 5, or an artificial replacement therefore, can pass. In embodiment where the band 810 is a rupture band, the band 810 has failed and thereby the caput femur 5, or an artificial replacement therefore, is held in place solely by the releasing member 801 which is adapted to release the caput femur 5, or an artificial replacement therefore, at a pre-defined strain. The medical device could be adapted to non-invasively be able to change from the first state to the second state and from the second state to the first state, when a pre-determined strain is placed on the band 810 and/or the releasing member 801, which enables the caput femur 5, or an artificial replacement therefore, to be replaced in the artificial acetabulum 65 without a surgical procedure.

FIG. 22 shows the hip joint in section according to an embodiment where the caput femur 5, or an artificial replacement therefore, and collum femur 6 have been replaced with a prosthetic part 818 fixated to the femoral bone 7, either with bone cement, or without. The prosthetic part 818 comprises an artificial caput femur 812 having a cavity 816 in which a rupture band 813 fixated to a fixation portion 814 of the artificial caput femur 812, and a fixating portion 815 of the artificial acetabulum 65. The cavity 816 is adapted to enable the artificial caput femur 812 to perform normal functional hip movements inside the artificial acetabulum 65. The rupture band 813 is adapted to hold the artificial caput femur 812 to the artificial acetabulum 65 in a first state, and release the artificial caput femur 812 from the artificial acetabulum when a pre-determined strain is placed on the rupture band 813.

FIG. 23 shows the embodiment of the medical device according to FIG. 22, in a second state in which the rupture band 813 has failed and thereby the artificial caput femur 812 is released from the artificial acetabulum 65. The rupture band 813 could be fixated to a fixation portion 814 of the artificial caput femur 812, and/or a fixating portion 815 of the artificial acetabulum 65 using: at least one screw, at least one pin, form fitting, welding, adhesive, pin, wire, a ball mounted into a bowl, a male portion of one part mounted into a female portion of the other part, a key introduced into a lock being portions of said parts, band, or other mechanical connecting members. The failing of the rupture band 813 is preferably caused by an abnormal movement of the hip joint, e.g. as the result of the patient falling.

FIG. 24 shows a prosthetic part 818 according to an embodiment where the prosthetic part 818 is fixated to the femoral bone 7 and comprises a caput femur 812 comprising a cavity 816 adapted to enable the hip joint to perform functional hip joint movements while in a first state held to the artificial acetabulum using an elastic bend 817 fixated to a fixation portion 814 of the artificial caput femur 812, and a fixating portion 815 of the artificial acetabulum 65, and a releasing member 801 according to the embodiment shown in FIGS. 9 and 10. The combination of the releasing member 801 and the elastic band 817 is adapted to, in a first state hold the prosthetic part 818 to the artificial acetabulum 65, and in a second state release the prosthetic part 818 from the artificial acetabulum 65. According to another embodiment (not shown) the prosthetic part is held to the artificial acetabulum 65 solely using the elastic band 817, of course also supported by the remainder of the hip joint capsule and the affected muscles.

FIG. 25 shows the embodiment of the medical device according to FIG. 24, in a second state in which the elastic band 817 is stretched such that the prosthetic part 818 is released from the artificial acetabulum artificial acetabulum 65. The elastic band 817 could be fixated to a fixation portion 814 of the artificial caput femur 812, and/or a fixating portion 815 of the artificial acetabulum 65 using: at least one screw, at least one pin, form fitting, welding, adhesive, pin, wire, a ball mounted into a bowl, a male portion of one part mounted into a female portion of the other part, a key introduced into a lock being portions of said parts, band, or other mechanical connecting members. The failing of the rupture band 813 is preferably caused by an abnormal movement of the hip joint, e.g. as the result of the patient falling. Preferably the elastic band 817 comprises an elastic part or section, which could be the entire elastic band 817, made from an elastic material, such as an elastic polymer material such as: a copolymer material such as polystyrene, poly(ethylene-butylene) or polystyrene. It is also conceivable that the material is a polyurethane elastomeric material, polyamide elastomeric materials and polyester elastomeric materials elastic copolymers of ethylene and at least one vinyl monomer such as, for example, vinyl acetates, unsaturated aliphatic monocarboxylic acids, and esters of such monocarboxylic acids. The elastic band 813 could comprise a barrier coating, which cannot be penetrated by body cells. Preferably, the barrier coating comprises a Parylene™ coating, or a biocompatible metal coating, such as gold, silver or titanium. According to other embodiments the elastic band comprises a spring type member, a combination of metal and plastic materials, a combination of metal and carbon based material or a combination of carbon and plastic based material.

FIG. 26 shows the hip joint in section in an embodiment where the medical device comprises a prosthetic part 819 adapted to be fixated to the femoral bone 7. The prosthetic part comprises an artificial caput femur which is adapted to comprise elastic elements 820 which act as a releasing member holding the artificial caput femur inside of the artificial acetabulum 65 fixated to the pelvic bone. The elastic elements 820 of the artificial caput femur, is preferably made of an elastic material, which for example could be an elastomeric polymer material or an elastic metal material. It is conceivable that the elastic material comprises an outer layer in connection with the artificial acetabulum 65 which is adapted to resist the wear from the contact with the artificial acetabulum surface. The elastic element is adapted to compress when a pre-determined strain is placed on the hip joint and thereby on the elastic elements 820. When the elastic elements 820 are compressed the artificial caput femur is released from the artificial acetabulum 65.

FIG. 27 shows the medical device according to the embodiment shown in FIG. 26, in a second state, in which the elastic element 820 has been compressed, following a pre-determined strain being placed on the medical device. The medical device is thereby placed in a second state, in which the artificial caput femur is released from the artificial acetabulum 65, wherein it has been held.

FIG. 28 shows an embodiment of the medical device in which the elastic elements 820 are further assisted by a spring 821 in connection with two elastic elements 820, the spring 821 is compressed alongside the elastic members 820, when a pre-determined strain is placed on the prosthetic part 819 comprising the artificial caput femur.

FIG. 29a shows the hip joint in section when a medical device for, in a first state, holding the caput femur 5, or an artificial replacement therefore, to the artificial acetabulum 65, and in a second state releasing the caput femur 5, or an artificial replacement therefore from the artificial acetabulum 65. The medical device is adapted to change from being in the first state to being in the second state at a pre-determined strain affecting the medical device by the connection with the pelvic bone 9 and the femoral bone 7, which reduced the risk of the patient fracturing the femoral bone 7 and/or the pelvic bone 9. The medical device comprises magnets 823 or magnetic material 823 placed in the artificial acetabulum 65, and magnets 822 or magnetic material 822 placed in the caput femur 5 or an artificial replacement therefore. According to one embodiment a magnet 823 is placed in the artificial acetabulum having its south pole directed towards the caput femur 5, or artificial replacement therefore, and a magnet 822 placed in the caput femur 5, or artificial replacement therefore, having its north pole directed towards the artificial acetabulum 65. However it is easily understood by the skilled in the art that only one of the sides needs to be magnetic whereas the other side merely needs to comprise magnetic material. Any combination of north and south ends and magnets/magnetic material is hence conceivable. The magnetic force described is adapted to hold the caput femur 5, or an artificial replacement therefore, in the acetabulum in normal use, enabling the hip joint to perform functional hip joint movements, and release the caput femur 5, or an artificial replacement therefore, from the artificial acetabulum 65 when a predetermined strain is exceeded.

FIG. 29b shows the medical device according to the embodiment of FIG. 29a in the second state, in which the caput femur 5, or an artificial replacement therefore, is released from the artificial acetabulum 65 as a result of a pre-determined level of strain being exceeded.

FIG. 30a shows the medical device according to another embodiment, in a first state, in which the medical device comprises a prosthetic part 818 fixated in the femoral bone 7. The prosthetic part 818 is separable along a separation line 860 being placed in the area of collum femur. The proximal portion of the prosthetic part is placed in the artificial acetabulum 65 and clasped therein such that stable fixation of the prosthetic part 818 to the pelvic bone 9 is enabled. By the prosthetic part being separable, the prosthetic part comprises two parts 861 and 862, wherein the first part 861 is adapted to be placed in an artificial acetabulum 65, and the second part 862 is adapted to be fixated to the pelvic bone 9. The first 861 and second 862 parts are connected to each other by means of a breakpin 863 placed in a hole in the prosthetic part 818. The break pin 863 is here a releasing member adapted to, in a first state hold said first piece 861 attached to said second piece 862, and in a second state, break to release said first piece 861 from said second piece 862. The breakpin 863 is adapted to break, and thereby changing from the first state to the second state, when a pre-determined strain is placed on the releasing member.

FIG. 30b shows the medical device according to the embodiment in FIG. 30a when the breakpin 863 has failed and thereby changing from the first state to the second state releasing the first piece 861 from the second piece 862.

FIGS. 30c and 30d shows the replacement of a failed breakpin 863 by removal of the pieces of the failed breakpin 863 (shown in FIG. 30c ) and replacing it with a new break pin 863 (shown in FIG. 30d ). Having the separation line 860 in the area of the collum femur and not in either of the fixations to the femoral bone 5 or the pelvic bone 9 makes it possible for the prosthetic part 818 to remain in its fixations in the femoral bone 5 and the pelvic bone 9 whilst still releasing the first part 861 from the second part 862 when a force exceeding a predetermined value is exceeded, such that the prosthetic hip joint can dislocate without injuring the fixations.

FIG. 31 shows, schematically, how the artificial acetabulum travels beyond the maximum diameter of the caput femur 5, or an artificial replacement therefore. That is, a cross-sectional distance of the largest opening 52 is smaller than the largest cross sectional distance of the caput femur 5 or an artificial replacement therefore

FIG. 32 shows the medical device according to an embodiment in which the second piece comprises: an inner surface 906, and an outer surface 907. The inner surface 906 comprises: a first point 908 a, a second point 909 a, a third point 908 b, a fourth point 909 b, a fifth point 908 c, and a sixth point 909 c, all points located on different places along a length axis of the inner surface. A first straight line 910 a, reaches from the first point 908 a to the second 909 a and is parallel to a second straight 910 b line reaching from the third point 908 b to the fourth point 909 b, which in turn is parallel to a third straight 910 c line, reaching from the fifth point 908 c to the sixth point 909 c. The first 910 a and the third 910 c straight lines are shorter than the second straight line, and the second straight line is positioned between the first and third straight lines.

FIG. 32c shows the medical device according to an embodiment where the releasing member 801 comprises an elastic wing of the medical device, which is assisted by an elastic or rupture band 810 encircling the medical device by enclosing the caput femur 5, or a prosthetic replacement therefore, in the medical device passing beyond the point of the caput femur 5, or an artificial replacement therefore, having a largest cross-sectional distance. The elastic or rupture band 810 is held in place to the medical device by means of the band 810 being placed in a groove along the circumference of the medical device. However, said groove could be assisted or replaced by an adhesive or a mechanical fixation element.

FIG. 32d shows the medical device when in its second state, in which the releasing member 801 releases the caput femur 5 or an artificial replacement therefore, from the medical device. In embodiments when the band 810 is an elastic band 810 it could be expanded, thereby enlarging the hole through which the caput femur 5, or a prosthetic replacement therefore, can pass. In embodiments where the band 810 is a rupture band, the band 810 fails and thereby the caput femur 5, or a prosthetic replacement therefore, is held in place solely by the releasing member 801 which is a part of the extending portion adapted to release the caput femur 5, or a prosthetic replacement therefore, at a pre-defined strain. The medical device could be adapted to non-invasively be able to change from the first state to the second state and from the second state to the first state, when a pre-determined strain is placed on the band 810 and/or the releasing member 801, which enables the caput femur 5, or a prosthetic replacement therefore, to be replaced in the medical device without a surgical procedure.

Opposite Embodiment

A general version of an opposite embodiment will now be described, the scope of the opposite embodiment is by no means limited to this particular version, on the contrary all of the above described embodiment can be used in the opposite embodiment.

FIG. 33 shows the hip joint in section when an artificial caput femur surface 112 is fixated to a surgically modified caput femur comprising a concave artificial acetabulum surface 110 placed in the surgically modified caput femur. According to the embodiment shown in FIG. 33 an elongated member 206 is used as a guiding rod, guiding and centering the artificial acetabulum surface, and the artificial caput femur surface in the hip joint. The convex hip joint surface 112 is secured by the releasing member 801 which is adapted to, in a first state, hold the artificial caput femur, and in a second state release the artificial caput femur, and change from a first to a second state when a pre-determined strain is exceeded. The releasing member is fixated to the surgically modified caput femur using screws 121. The surface of the locking element 117 and the concave hip joint surface 117 is placed in connection with the convex hip joint surface and could be made of a friction reducing material such as PTFE or a self lubricating powder material. However it is also conceivable that the connecting surfaces are lubricated using an implantable lubrication system adapted to lubricate the medical device after said medical device has been implanted in the human patient, a solution conceivable in all of the above described embodiments. According to the embodiment shown the elongated member 206 is inserted through the femoral bone, however according to other embodiments, not shown, the elongated member is positioned inside of the hip joint from the acetabulum side.

FIG. 34 shows the placing of a prosthetic part 118 adapted to occupy the hole 18 created in the pelvic bone 9. The prosthetic part 118 comprises supporting members 119 adapted to be in contact with the pelvic bone 9 and assist in the carrying of the load placed on the medical device from the weight of the human patient. Furthermore FIG. 34 shows the fixation of a nut 120 to the attachment rod 113, which in turn is guided by the elongated member 206 which acts as a guiding rod.

FIG. 35 shows the hip joint in section when all the elements of the medical device has been fixated in the area of the hip joint or its surroundings. The prosthetic part 113 adapted to occupy the hole 18 in the pelvic bone 9 is here fixated with screws 121, however these screws 121 could be assisted or replaced by an adhesive which could be applied to the surface S between the prosthetic part and the pelvic bone 9. The elongated member 206 which acts as a guiding rod has been retracted through the incision in the thigh.

The elastic or flexible part, piece or portion of any of the embodiments herein could comprise an elastic polymer material such as: a copolymer material such as polystyrene, poly(ethylene-butylene) or polystyrene. It is also conceivable that the material is a polyurethane elastomeric material, polyamide elastomeric materials and polyester elastomeric materials elastic copolymers of ethylene and at least one vinyl monomer such as, for example, vinyl acetates, unsaturated aliphatic monocarboxylic acids, and esters of such monocarboxylic acids. The elastic band 813 could comprise a barrier coating, which cannot be penetrated by body cells. Preferably, the barrier coating comprises a Parylene™ coating, or a biocompatible metal coating, such as gold, silver or titanium. According to other embodiments the elastic band comprises a spring type member, a combination of metal and plastic materials, a combination of metal and carbon based material or a combination of carbon and plastic based material.

The artificial acetabulum, according to any of the embodiments, could comprise one or more parts which could be fixated to the pelvic bone using at least one screw, at least one pin, at least one portion of at least one of the parts adapted to be introduced into the other part, the parts being adapted to be sliding into the other part, form fitting, welding, adhesive, pin, wire, a ball mounted into a bowl being portions of said parts, a male portion of one part mounted into a female portion of the other part, a key introduced into a lock being portions of said parts, band, or other mechanical connecting members.

FIG. 36a shows an embodiment of a locking/releasing member 116, wherein the locking/releasing member 116 comprises a surface 1353 adapted to be in contact with the artificial convex hip joint surface (112 in FIG. 36b ), being a first piece, and slide against the hip joint surface, the locking member 116 is adapted to, in a first state, lock the artificial caput femur 112 to the artificial acetabulum surface (1340 in FIG. 36b ), and in a second state, release said artificial caput femur 112 from said artificial acetabulum 1340. The locking/releasing member 116 is adapted to change from the first to the second state when a predetermined amount of strain is placed on the locking/releasing member 116. The locking/releasing member 116 according to the embodiment shown in FIG. 28b , comprises four holding members, here being elastic portions 1351, and the locking/releasing member 116 is adapted to change from the first to the second state using the elasticity of the elastic portions 1351. The locking member 116 is adapted to be fixated to the femoral bone 7 using screws adapted to be placed in holes 1352 adapted therefor. According to another embodiment (not shown) the holding members 1351 comprises at least one holding member adapted to roll against the first piece, being the artificial convex hip joint surface 112.

FIG. 36b shows the hip joint in section when the two state locking/releasing member 116 locks the artificial caput femur 112 in the artificial acetabulum 1340. The two state locking/releasing member 116 is fixated to the femoral bone 7 using screws 121, and is here shown in its first state in which the locking/releasing member 116 locks the artificial caput femur 112 to the artificial acetabulum 1340.

FIG. 36c shows the hip joint in section according to the embodiment of FIG. 36b , but when the two state locking/releasing member 116 is in its second state, in which the locking/releasing member 116 releases the artificial caput femur 112 from the artificial acetabulum surface 1340. The construction with the locking/releasing member 116 reduces the risk of strain placed on the artificial joint injuring the fixation points, i.e. the contact with bone; it further enables the artificial joint to be non-invasively relocated in case of luxation.

FIG. 36d shows an alternative embodiment of the two-state locking/releasing member 116, in which the two-state locking/releasing member 116 further comprises an elastic band 1361 adapted to encircle the artificial caput femur 112, when implanted. The elastic band 1361 could be an elastic polymer band, such as a polyurethane or silicone band.

FIG. 36e shows a hip joint in section when the two-state locking/releasing member 116 has been implanted, and being in its first state. The two-state locking/releasing member 116 is fixated to the femoral bone 7 using screws 121.

FIG. 36f shows the implantable device comprising the two-state locking/releasing member 116 when in its second state, i.e. in the state in which the locking/releasing member 116 is adapted to release the artificial caput femur 112 through the elastic band 1361 encircling the artificial caput femur 112 is stretched so that the artificial caput femur 112 can exit from the artificial acetabulum 1340. The construction with the locking/releasing member 116 reduces the risk of strain placed on the artificial joint injuring the fixation points, i.e. the contact with bone; it further enables the artificial joint to be non-invasively relocated in case of luxation.

The locking/releasing member 116 described with reference to FIGS. 36a-36f are depicted in embodiments with a large hole in the pelvic bone 9 occupied by a prosthetic part 118, however, it is equally conceivable that the two state locking/releasing member 116 is used in embodiments with a small hole in the pelvic bone 9, for a less invasive procedure, it is furthermore conceivable that the all of the embodiments disclosed of the medical device could be installed during conventional open hip joint surgical procedure, penetrating the hip joint capsule. In this case the two state locking/releasing member 116 could be a part of a full prosthesis, such as the prosthesis disclosed with reference to FIGS. 22-28.

FIG. 36g shows an embodiment of a locking/releasing member 116, wherein the locking/releasing member 116 comprises a spring 1371 creating the elasticity needed to change from a first state to a second state for releasing the artificial caput femur 112 from the artificial acetabulum 1340. The locking/releasing member 116 is adapted to change from the first to the second state when a predetermined amount of strain is placed on the locking/releasing member 116. According to the embodiment shown in FIG. 36g the medical device further comprises a calibration screw 1372 placed in connection with the spring 1371 for calibrating the elasticity and thereby the amount of strain required for the locking/releasing member to change from the first to the second state.

FIG. 36h shows an embodiment of the locking/releasing member in which the locking/releasing member comprises four rupture pins 1373 adapted to fail at a pre-determined strain, for allowing the locking/releasing 116 members to change from the first to the second state. The pins are, according to this embodiment, made from a brittle material which could be adapted for the particular patient. In other embodiments (not shown) the rupture pins 1373 could be replaced by a rupture band, similar to the elastic band, but adapted to fail at a pre-determined strain, or a rupture band placed centrally, such as disclosed with reference to FIG. 23.

FIG. 36i shows the hip joint in section when an artificial caput femur 1375 a,b comprising two parts 1375 a and 1375 b is adapted to be interconnected to form an interconnected artificial caput femur. Each of the two artificial parts 1375 a, 1375 b, furthermore comprises a fixating portion 1374 a, 1374 b adapted to be fixated to the inside of the acetabulum 8. The artificial caput femur is, after the interconnection, adapted to be placed in an artificial concave acetabulum 1340 placed in the proximal portion of the femoral bone 7, for creating a functional hip joint in an opposite embodiment.

FIG. 36j shows the hip joint in section when the interconnected artificial caput femur 1375 has been placed in the acetabulum 8, and been fixated using the fixating portion 1374. The locking/releasing member 116 has been placed onto the artificial caput femur 1375 using the spring 1371 creating the elasticity required to enable the artificial caput femur 1375 to be placed such that the locking/releasing members clasps the artificial caput femur 1375.

FIG. 36k shows the hip joint in section when the two state locking/releasing member 116 locks the interconnected artificial caput femur 1375 in the artificial acetabulum 1340. The two state locking/releasing member 116 is fixated to the femoral bone 7 using screws 121, and is here shown in its first state in which the locking/releasing member 116 locks the artificial caput femur 112 to the artificial acetabulum 1340.

FIG. 36m shows the hip joint in section according to the embodiment of FIG. 36k , but when the two state locking/releasing member 116 is in its second state, in which the locking/releasing member 116 releases the artificial caput femur 112 from the artificial acetabulum surface 1340, by means of the spring 1371 creating the required elasticity. The construction with the locking/releasing member 116 reduces the risk of strain placed on the artificial joint injuring the fixation points, i.e. the contact with bone; it further enables the artificial joint to be non-invasively relocated in case of luxation.

Please note that any embodiment or part of embodiment as well as any method or part of method could be combined in any way. All examples herein should be seen as part of the general description and therefore possible to combine in any way in general terms. 

1.-48. (canceled)
 49. A medical device for implantation in a hip joint of a patient, said medical device comprising: a. a first piece, wherein i. said first piece is adapted to be fixated to the femoral bone, and ii. said first piece comprises a convex contacting surface adapted to be partially placed inside a concave contacting surface, b. a second piece, wherein i. said second piece is adapted to be fixated to the pelvic bone, and ii. said second piece comprises a concave contacting surface adapted to partially, surround said convex contacting surface of said first piece, when implanted, and c. a releasing member adapted to, when implanted, in a first state hold said first piece attached to said second piece, and in a second state release said first piece from said second piece, and wherein said releasing member is adapted to change from said first state to said second state when a predetermined strain is placed on said releasing member by the connection with the first or second piece, when implanted, and wherein said medical device comprises a calibration member for calibrating the pre-determined strain required for said releasing member to change from said first state to said second state.
 50. The medical device according to claim 49, wherein said first piece comprises a ball shaped piece and said second piece comprises a bowl shaped piece, and wherein said ball shaped piece is adapted to be placed in said bowl shaped piece to replace a functioning hip joint.
 51. The medical device according to claim 50, wherein said ball shaped piece is adapted to be fixated in said bowl shaped piece using said releasing member.
 52. The medical device according to claim 49, wherein said releasing member is adapted to change from said first state to said second state and from said second state to said first state without requiring any invasive steps, when a predetermined strain is placed on said releasing member.
 53. The medical device according to claim 49, wherein said second piece of said medical device comprises said releasing member.
 54. The medical device according to claim 49, wherein said releasing member comprises at least one of; a bendable portion, a flexible portion, a compressible portion, a movable portion, a movable part, an elastic material, a spring, an elastic band, a magnet adapted to hold said first piece to said second piece, and a rupture device adapted to fail at a pre-determined strain.
 55. The medical device according to claim 54, wherein said elastic band is adapted to at least partly encircle said ball shaped piece.
 56. The medical device according to claim 49, wherein said releasing member comprises multiple holding members.
 57. The medical device according to claim 56, wherein said holding members comprises at least one holding member adapted to slide against said first piece.
 58. The medical device according to claim 56, wherein said bedding members comprises at least one holding member adapted to roll against said first piece.
 59. The medical device according to claim 49, wherein said calibration member is a calibration screw.
 60. The medical device according to claim 54, wherein said rupture device comprises a rupture pin. 